Click for next page ( 4

The National Academies of Sciences, Engineering, and Medicine
500 Fifth St. N.W. | Washington, D.C. 20001

Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement

Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 3
to Saving Lives.1 This document provides states with The objective of black spot analysis is to find locations guidance for complying with the safety provisions of that exhibit unusually high crash frequencies or crash the legislation. A key requirement of SAFETEA-LU rates. The crash data are then analyzed and problem is that each state must prepare an SHSP that docu- locations are prioritized and ranked. Infrastructure- ments its process for reducing the number of fatal based countermeasures, such as improving intersec- and serious-injury crashes across the entire roadway tion geometry or traffic control devices, are then system, regardless of jurisdiction (management by applied to address safety deficiencies at these specific state or local agency). locations. FHWA also implemented a policy change to The technical analysis normally considers all HSIP that revised the objective of the program from crashes because severe crashes are too rare (fatal and reducing highway crashes in general to specifically A-injury crashes generally account for less than 2% emphasizing the prevention of fatal and serious- of all crashes), random, and widely distributed geo- injury crashes. This change in emphasis--from all graphically to efficiently identify specific problem crashes to severe crashes--presents a new challenge locations. However, the use of all crashes as the to the professionals implementing safety programs safety performance measure generally points ana- within the states. Because of the random, widely lysts toward locations with high traffic volumes in distributed nature of severe crashes, it is difficult to urban areas. As a result, common black spot loca- identify specific at-risk locations. For example, in tions are intersections, particularly signalized inter- Minnesota, approximately 33% of fatal crashes sections along multi-lane urban arterial roadways (190 per year) involve a single vehicle running off (see Figure 2). the road, 75% of these (145 per year) are in rural Black spot analysis is clearly a necessary compo- areas, and 62% of these (90 per year) are on the local nent of a comprehensive program to improve the system. However, this system is made up of over safety of the nation's highways. In urban areas, where 45,000 miles of two-lane highways, which results in traffic volumes and crash frequencies are high, black a density of 0.002 fatal road-departure crashes per spot analysis will likely continue to be the most com- mile per year. This statistic raises two questions: are mon method utilized for allocating safety resources. all of these miles equally at risk for severe crashes Intuitively, it seems to make sense to target limited and, if not, how can the locations most at risk for safety funds at locations that have documented safety severe crashes be identified as candidates for safety deficiencies. However, black spot analysis has not investment? To address these questions and truly proven effective at reducing the fatal and serious- focus on reducing the most severe crashes, new injury crashes that are widely distributed across the approaches and analytical techniques are required. roadway system--crashes that are not concentrated CURRENT METHODS FOR ALLOCATING SAFETY RESOURCES There are currently two methods available to the states for allocating safety resources. These methods are commonly referred to as (1) the "black spot" analysis method and (2) the "systematic" method. Black Spot Analysis Black spot analysis has been most commonly used by transportation agencies in the United States for identifying candidate locations for safety investment. 1 FHWA, NHTSA, FMCSA, FTA, and FRA. Strategic High- way Safety Plans: A Champion's Guide to Saving Lives. U.S. Figure 2 Example of a typical urban black spot DOT, 2006. location. 3